Korean Journal of Optics and Photonics (한국광학회지)

Optical Society of Korea (한국광학회)
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Redefinition of the SI Base Units with Fundamental Constants

기본상수를 이용한 SI 기본단위의 재정의

  • Lee, Ho Seong (Center for Time and Frequency Metrology, Korea Research Institute of Standards and Science)
  • 이호성 (한국표준과학연구원 시간표준센터)
  • Received : 2019.05.07
  • Accepted : 2019.06.04
  • Published : 2019.08.25
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Abstract

Revision of the International System of Units (SI) in terms of fundamental constants was achieved by the 26th General Conference on Weights and Measures (CGPM) in November 2018. Four base units (kilogram, ampere, kelvin, and mole) of SI were redefined by fixing the values of the Planck constant h, elementary charge e, Boltzmann constant k, and Avogadro constant $N_A$ respectively. In this paper the scientific principle for redefining the kilogram from the Planck constant with the Kibble balance is explained as an example. The revised SI takes effect on May 20, 2019.

기본상수를 이용한 국제단위계 개정이 2018년 11월에 개최된 제26차 국제도량형총회에서 채택되었다. 국제단위계에 속한 4개의 기본단위(킬로그램, 암페어, 켈빈, 몰)가 각각 그 값이 고정된 플랑크 상수 h, 기본 전하 e, 볼츠만 상수 k, 아보가드로 상수 $N_A$를 기반으로 재정의되었다. 이 논문에서는 키블 저울을 이용하여 플랑크 상수로부터 킬로그램을 재정의한 원리를 설명한다. 개정된 국제단위계는 2019년 5월 20일부터 발효된다.

Keywords

KGHHBU_2019_v30n4_133_f0001.png 이미지

Fig. 1. Operational principle of the Kibble balance: Fem and Fm mean an electromagnetic force and a mechanical force, respectively. When the two forces are balanced, we can find out the mass through two operational modes.

KGHHBU_2019_v30n4_133_f0002.png 이미지

Fig. 2. Values of the Planck constant h and the CODATA 2017 value. The inner band is ± 2 × 10-8 and the outer band is ± 5 × 10-8 (KB: Kibble balance; XRCD: x-ray-crystal-density)[13].

KGHHBU_2019_v30n4_133_f0003.png 이미지

Fig. 3. Relationship among the seven defining constants and the seven SI base units: the unit from which an arrow starts is included in the definition of the unit which the arrow indicates.

Table 1. The CODATA recommended values and relative standard uncertainties for the Planck constant from 1998 to 2014

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Table 2. The CODATA 2017 adjusted values of h, e, k, and NA[13].

KGHHBU_2019_v30n4_133_t0002.png 이미지

Table 3. The CODATA 2017 values of h, e, k, and NA for the revision of the SI[13].

KGHHBU_2019_v30n4_133_t0003.png 이미지

Table 4. Fundamental constants having no uncertainty by the revision of the SI

KGHHBU_2019_v30n4_133_t0004.png 이미지

Table 5. Quantities having new uncertainty by the revision of the SI

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Table 6. SI derived units with special names and symbols which can be defined by the seven defining constants

KGHHBU_2019_v30n4_133_t0006.png 이미지

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